PRELIMINARY OPERATIONS 



85 



(b) Insertion of Tracheal and Carotid Cannulas; Isola- 

 tion of Vagi and External Jugular Vein. As soon as the 

 animal is securely fastened down, a median incision is 

 made in the skin and fascia over the trachea as shown in 

 Fig. 83. Observe with great care the teclmic shown in the 

 illustration and follow it carefullv. Next take two aneurism 



Fig. 82. Method of fastening the hind limbs. 



needles and separate the mesial borders of the sternohyoid 

 muscles as shown in Fig. 84. This brings into view the 

 trachea (Fig. 85) with the carotid sheath containing the 

 carotid artery and vago-sympathetic nerves on each side 

 (posteriorly) of the wind-pipe. Next take an aneurism 

 needle and hook it under the trachea as shoAvn in Fig. 86. 

 With the largest forceps pick up by one end the heavy 

 twine to tie in the trachea! cannula. While holding this 

 in the forceps lift up the trachea with the aneurism needle 

 and push the forceps (holding the twine) through the 



